The present invention relates to a hot standby system. Particularly, the present invention relates to consistency check of a shared disk in a hot standby system having a shared disk accessible from active and standby computers and to a switching control between the computers.
Recently, in the field of online transaction processes, hot standby structure systems having a shared disk accessible from active and standby computers are used to improve availability of the online transaction processes.
For example, Japanese Published Unexamined Patent Application No. 1998-289122 discloses this type of hot standby system. The disclosure is as follows. One disk is connected to each of active and standby computers. In normal operation, when data is updated in the active computer, updated data is sent to the standby computer via a network so that data is updated in the standby computer in the same way as the active computer. When a failure occurs in the active computer, the standby computer takes over jobs as a new active computer, and the former active computer functions as a standby computer. After recovery from the failure, updated data after the takeover is sent from the new active computer to a new standby computer, so that synchronization is executed in a shared disk. According to this conventional technique, when the standby computer is switched, jobs can be taken over without further synchronizing data in both disks, so that a time up to a restart of the jobs can be shortened.